CHARACTERIZATION OF THE 97 AND 103-KDA FORMS OF STARCH BRANCHING ENZYME FROM POTATO-TUBERS

N-Terminal analysis, peptide mapping and partial peptide sequencing of the 97 and 103 kDa forms of starch branching enzyme from potato tuber s showed that the two forms are highly related. A comparison with sequ ence data in the literature showed that these forms belong to the star ch branching enzyme isoform I family. An internal cDNA fragment was ob tained using PCR technology on potato tuber RNA with two oligonucleoti de primers constructed from the peptide sequence data. Southern blot a nalysis using the PCR fragment as probe showed that there is only one gene locus encoding this isoform of the enzyme in Solanum tuberosum as well as in Solamun commersonii.